The present invention relates to a method for checking the security of installation of a joining element which is to be fixed to a component by way of an adhesive connection, wherein the adhesive is withdrawn from an adhesive receptacle and can be cured by irradiation with light from a light emitter. The invention also relates to a device for carrying out the method, having a joining head which is arranged on a robot arm, and having a gripper for withdrawing joining elements from the device, wherein the joining elements are arranged in storable fashion in the device and can be conveyed by an advancing device into a dispensing position.
The invention also relates to a device having a first and a second adhesive receptacle, which are connected by way of a respective fluid line to an adhesive applicator.
A generic device for accommodating joining elements is often a store or a magazine which can, in particular, be fastened to a joining head.
A generic device having a first and a second adhesive receptacle is often a provision or loading station with a dispenser.
The joining elements may, as seen in cross section, have a T-shaped form with a disk and a bolt, wherein an adhesive can be applied to the disk. Thus, the disk of the T-shaped joining element can be fixed to the surface of a component by way of an adhesive connection, and a second component can be fixed to the bolt by way of a screw connection or a snap-action connection.
In the manufacturing sector, in particular in the series manufacture of motor vehicles, aircraft, light aircraft or vehicles of any other type, use is nowadays increasingly made of components, for example structural components in the bodyshell structure, composed of so-called fiber composite materials. A fiber composite material of said type is, for example, carbon fiber-reinforced plastic, also referred to as CFRP. The advantages of CFRP in relation to metals include, inter alia, a low mass with a high strength. For the connection of such CFRP components to metallic components, however, special requirements must be observed. CFRP components cannot readily be provided with a bore and connected to a metal component, as the connecting point between the CFRP and the metal component is susceptible to corrosion.
Therefore, for the connection of a CFRP component to a metal component, use is normally made of a T-shaped joining element with a disk composed of plastic and with a threaded bolt composed of metal, wherein the disk is adhesively bonded to the CFRP component, and the threaded bolt is screwed to the metal component.
DE 10 2011 009 259 A1 discloses a placement system which has a joining head for applying joining elements to a component by way of an adhesive connection. Furthermore, this document discloses a method for mounting joining elements onto the component.
A joining head of this type normally has a gripper with a light emitter, a pivot arm, a magazine and a fastening plate. In this case, the joining head may be fastened by way of the fastening plate to a robot arm. The gripper with the light emitter is fastened to the pivot arm, which gripper individually withdraws the joining elements that are stored in storage rails in the magazine. The pivot arm of the joining head then places the individually withdrawn joining element onto a component provided therefore. The light emitter subsequently ensures that the adhesive that is applied to the joining element is cured by irradiation with light.
After the withdrawal of the joining element from the dispensing position, another joining element of the storage rail is guided into the dispensing position of the magazine. This follow-up transportation or follow-up feed of a further joining element into the dispensing position of the magazine is performed by way of an expanding spring.
When the final joining element has been withdrawn from the magazine by the pivot arm by way of the gripper and applied to the component surface, the magazine of the joining head can subsequently be coupled to a loading station.
After the coupling process is complete and the multiplicity of joining elements have been transferred from the loading station to the magazine, the pivot arm of the joining head can, in the manner described above, resume the process of withdrawing joining elements from the magazine and applying them onto the component provided therefore.
In the method mentioned above for applying a T-shaped joining element onto a component surface, adhesive is initially applied to the joining elements. The joining elements are placed into the magazine. The magazine is subsequently moved in its longitudinal direction. And, the gripper withdraws a joining element from the magazine in order to mount it on the component, whereafter the curing source is finally activated.
DE 10 2009 057 332 A1 discloses a loading station with a dispenser, in which the application of adhesive to the disk of the T-shaped joining element is performed by use of the dispenser or the adhesive applicator. The joining elements can be buffer-stored in rails of a buffer store of the loading station and/or moved into a magazine.
The magazine takes on the T-shaped joining elements from the loading station, wherein the joining element can, in the dispensing position of the magazine, be manually or automatically withdrawn from the magazine by the gripper and applied manually, or automatically by way of a robot, to the component surface at its predetermined processing position.
The follow-up transportation or follow-up feed of a further joining element into the dispensing position of the magazine is performed by way of a spring-preloaded slide.
In the abovementioned method for applying a T-shaped joining element to a component surface, adhesive is applied to the joining elements. The joining elements are placed into a buffer store or directly into a magazine. The magazine and gripper are pivoted such that the gripper can withdraw a joining element from the magazine and apply said joining element to the component surface. And, the joining element is finally irradiated with light such that the adhesive cures.
The described methods for fastening joining elements to a component surface have the disadvantage that they do not have any steps for checking quality or security of installation during the course of the fastening process. The methods are therefore susceptible to errors and exhibit low process reliability.
The present invention is therefore based on the object of providing a method for applying joining elements to a component, which method, with regard to industrial series manufacture, provides steps during the course of the fastening process for checking the security of the installation, for quality assurance and for increasing process reliability and reducing susceptibility to errors. It is also sought to provide a device for carrying out the method and for arranging on a joining head of a robot arm, by which device reduced susceptibility to errors and increased process reliability are achieved with regard to the application of joining elements to components in industrial series manufacture.
It is a further object of the present invention to provide a device for applying adhesive, by which device process reliability is increased and downtime is reduced.
This and other objects are achieved according to the method, the device for carrying out the method, and a device for applying adhesive, in accordance with embodiments of the present invention.
The invention provides a method for checking the security of installation of a joining element which is to be fixed to a component by way of an adhesive connection, wherein the adhesive is withdrawn from an adhesive receptacle and can be cured by irradiation with light from a light emitter. The method includes the following acts:
a) the fill level of the adhesive receptacle is monitored and, if a lower threshold value of the detected fill level of said adhesive receptacle is reached, fluidic connection device of a second adhesive receptacle, whose fill level of adhesive is higher than that of the former adhesive receptacle, is actuated in order to produce a fluidic connection to an adhesive dispenser;
b) the intensity of the light radiated by the light emitter is checked by at least one sensor, and a signal is output if a threshold value of the light received by the sensor is undershot.
The checking of the fill level of the adhesive receptacle with regard to a lower threshold value makes it possible for the impending empty state of the adhesive receptacle to be identified in good time. When the threshold value of one adhesive receptacle is reached, a switch to a second adhesive receptacle is performed. The switch to the second adhesive receptacle may be performed, for example, by way of a pneumatic valve and serves the purpose of avoiding standstill times and thus an interruption in the execution of the method.
Through the checking of the light intensity of the light and the outputting of a signal upon a threshold value being reached, reliable curing of the adhesive during their radiation with light is achieved.
The two processes, of threshold value monitoring of the adhesive receptacle and checking of the light radiated by the light emitter, are necessary at least for uninterrupted application of adhesive to the joining elements and secure fastening of the joining elements to the component.
In one advantageous refinement of the method for checking security of installation, it is provided that the adhesive is withdrawn from, in each case, one of the two adhesive receptacles whose detected fill level exceeds the lower threshold value.
The purpose of the adhesive being withdrawn from, in each case, one of the adhesive receptacles consists in preventing a situation in which, during the execution of the fastening method, an empty state of the adhesive receptacle can arise prematurely and the joining process is interrupted. The method is thus suitable for series manufacture.
It is therefore not sufficient to provide one adhesive receptacle which, during normal operation, provides adequate adhesive for the execution of the fastening method. For uninterrupted operation with adhesive application, it is necessary for the state of the adhesive receptacle, for example the fill level and the pressure, to be monitored and, if necessary, for a switch to be made to a second adhesive receptacle.
In one advantageous refinement of the method for checking security of installation, it is provided that monitoring of the two adhesive receptacles with regard to the lower threshold value being reached is performed by way of at least one sensor.
In one advantageous refinement of the method for checking security of installation, it is provided that, for each joining point on the component, joining parameters for the joining element which is to be fixed at the joining point by way of the adhesive connection are defined.
To allow for different spatial orientation of joining points on the CFRP component, it is provided that different joining parameters can be defined for joining elements which are to be mounted in different spatial orientations.
These joining parameters are, for example, the orientation of the pivot arm and the mounting pressure on the joining element, and the force threshold value and the mounting time implemented for the mounting of the joining element onto the component.
In one advantageous refinement of the method, it is provided that the checking of the intensity of the light radiated by the light emitter and of the temperature is performed during an ongoing process of irradiation of the joining element.
To check the intensity of the light radiated by the light emitter during a process of irradiation of a joining element, the light may be captured, and fed to a spectrometer, at a defined distance from the outlet surface of the light emitter. In this way, the light intensity of the light radiated by the light emitter can be measured, and compared with a threshold value of the light intensity, during the irradiation of the joining element.
In one advantageous refinement of the method, it is provided that, after being irradiated with light, the joining element is subjected to a predetermined tensile force by way of a gripper.
To check whether the adhesive at the joining point has cured after the process of irradiation by the light emitter, an inspection is performed by way of the bolt of the joining element being subjected to a tensile force after the curing of the adhesive. In this case, low tensile forces are adequate, as these enable situations in which curing of the adhesive has not occurred to be identified, and at the same time, no damage is caused to joining elements that have been mounted correctly.
In one advantageous refinement of the method, it is also provided that the checking of the intensity of the light radiated by the light emitter is performed at predetermined time intervals.
The predetermined time intervals for the checking of the intensity of the radiated light may be stored in a control unit as a number of irradiation processes.
The measurement of the intensity of the light radiated by the light emitter may be performed between individual irradiation processes. In this case, the light emitter is activated for a certain time period, and the light intensity is detected by way of a sensor and compared with a threshold value.
The invention also provides a device for carrying out the method, which device is provided for arrangement on a joining head of a robot arm with a gripper for withdrawing joining elements from the device, wherein the joining elements are arranged in storable fashion in the device and can be conveyed by an advancing device into a dispensing position, and wherein the advancing device has at least one actuating cylinder which has an actuating piston which can be acted on by way of fluid and which conveys the joining elements.
For the purposes of conveying the joining elements in the direction of the dispensing position, the actuating piston is acted on with a fluid via feed lines. By being acted on with fluid, the actuating piston is caused to move in the advancing direction in the axial longitudinal direction of the actuating cylinder.
In this way, it is possible for the device for accommodating joining elements to provide permanently exact and precisely reproducible advancing movements of the actuating piston, in particular over a very large number of successive advancing movements, such as is customarily the case in the series manufacture of structural and functional parts. Thus, the joining elements are always conveyed in the direction of their dispensing position in an exact and reliable manner.
The invention furthermore provides a device having a first and a second adhesive receptacle, which are connected by way of a respective fluid line to an adhesive applicator, wherein each fluid line has a fluid shut-off valve, and the fluid lines issue into a common feed line to the adhesive applicator.
The use of two adhesive receptacles, the monitoring of the fill level of an adhesive receptacle with regard to a threshold value and the switching to a second adhesive receptacle in the event of the threshold value being undershot make it possible for the device for adhesive application to operate in uninterrupted fashion. In this way, the ongoing operation of adhesive application does not need to be interrupted, such as in the case of operation using only one adhesive receptacle. This in turn contributes to an increase in process reliability.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.